Portable flameless heaters are currently used in a variety of applications, for example heating comestible items. For example the United States Army uses a flameless ration heater (FRH) rather than a portable camp-stove to heat a pre-packaged MRE (meal ready to eat) eight-ounce (approximately 227 grams) field ration. The FRH consists of a super-corroding magnesium/iron mixture sealed in a waterproof pouch (total FRH weight is approximately 22 grams). To operate a FRH, the pouch is opened into which the MRE is inserted, and approximately 58 grams of water is added to a fuel-containing portion of the FRH pouch surrounding the MRE to initiate the following reaction:Mg+2H2O→Mg(OH)2+H2 
Based upon the above reaction of the fuel, the MRE temperature is raised by approximately 100° F. in less than 10 minutes. The maximum temperature of the system is safely regulated to about 212° F. by evaporation and condensation of water vapor.
The current FRH, while effective for its intended purpose, produces hydrogen gas as a byproduct, generating safety, transportation, storage and disposal concerns, and making it less suitable for use in consumer sector applications where accidental misuse could lead to fire or explosion.
Also, the water required for reaction, in addition to being heavy and spacious, is typically obtained from a soldier's drinking water supply, which is often limited. Addition of the water can also be an inconvenient additional step in the process of activating the FRH.
Self-heating food packaging products are also available in the consumer market. These products use the heat of hydration from mixing “quicklime” (calcium oxide) and water (CaO+H2O→Ca(OH)2) which does not generate hydrogen. With water present the peak temperature is similarly limited to 212° F. but even neglecting the weight of packaging and water, the specific energy of the system is low (approximately 1.2 kJ per gram of CaO). These and other self-contained systems must also provide some means of mixing the segregated reactants adding further complexity and bulk. Measurements on some commercial self-heating packaged food products are shown in Table 1.
TABLE 1Food product (net)Total package (gross)SpecificVolumeVolumeenergy ofWeight (g)(ml)Weight (g)(ml)heater (kJ/g)Coffee3002955516000.34Beef stew4254818839630.13
While quicklime based heaters may offer greater safety than the Mg based heaters, quicklime heaters significantly lower specific energy and cause the weight and size of the heater to approach that of the object being heated, reducing portability.
In addition to the water-based heaters described above, it is known to utilize oxygen-based heaters. Oxygen-based heaters, such as those described in U.S. Pat. Nos. 5,984,995, 5,918,590 and 4,205,957, have certain benefits over water-based heaters.
First, oxygen-based heaters do not require the addition of water to generate heat. Second, because the oxygen-based heater generates heat only in the presence of oxygen, the reaction may be stopped by preventing oxygen access and then restarted at a later time.
Despite the advantages of oxygen-based heaters, there is still a need for improved oxygen-based heaters, as well as methods of manufacturing same.
In addition, it would be beneficial to use such an oxygen-based heater in the heating of an object such as sanitary wipes and/or baby wipes, as well as utilize such heaters in a housing for heating the sanitary wipes/or baby wipes.